Develop a generally applicable method for assigning genes to scriptons. Utilize the fact that UV-lesions on DNA terminate the transcription and prevent RNA synthesis beyond the UV-lesion up to the next promotor. The target size for gene inactivation is, therefore, given by the distance between promotor and the promotor distal end of the gene. Determine gene survival by (1) complementation, (2) by radioactive labeling and analysis on SDS-acrylamide gels of the gene products. Assign genes to the classes of immediate early and delayed early mRNA in T4. Determine by labeling and electrophoresis which gene products are encoded in immediate early and delayed early mRNA. Determine the various causes for the delayed appearance of early gene products. Test whether there is a requirement for promotor activation or terminator inactivation. Terminator inactivation would place delayed early genes promotor distal. Promotor activation would place some delayed early genes promotor proximal. Distinction between the two cases will be made by RNA-DNA hybridization-competition experiments utilizing mRNA deleted in distal genes by UV irradiation of the template DNA. We propose exploratory studies into translational control of bacteriophage gene expression by modifying factors which determine the selective translation of early and late T4 mRNA. Investigate the differential translation of genes within the same scription. We propose to combine genetic alterations of the translational modes with in vitro studies of protein synthesis involving normal and modified components.